Toning composition for direct positive paper



United States Patent 3,515,555 TONING COMPOSITION 012 DIRECT POSITIVE PAP R Henry J. Fassbender, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey N Drawing. Filed Mar. 8, 1967, Ser. No. 621,460

Int. Cl. G031: 7/00 US. CI. 96-52 8 Claims ABSTRACT OF THE DISCLOSURE Toning compositions containing an inorganic sulfurcontaining compound, an alkali metal hydroxide, a thioamine or derivative thereof and an alkali metal iodide are used to produce a warmer tone than previously obtainable on direct positive photographic paper.

This invention relates to novel compositions useful for toning developed images of direct positive photographic emulsions and, particularly, to the use of the novel compositions for producing brown tones on direct positive photographic emulsions after exposure and development thereof, which emulsions normally produce a black and white image. More particularly, the invention is directed to the production of warm brown tones on direct positive photographic emulsions by treating such emulsions after development with a toning composition comprising an inorganic sulfur-containing compound, an alkali metal hydroxide, a thioamine or derivative thereof and an alkali metal iodide.

It is known that photographic images can be produced on silver halide direct positive emulsions by methods in which the exposed emulsion is chemically modified to produce a direct positive image. Thus, in the fields of industrial photography, and particularly in portrait and pictorial photography, the normal processing of direct positive photographic emulsions comprises developing the film, bleaching the developed image, clearing and neutralizing the bleached image, re-exposing the emulsion and then redeveloping the image in the original developer. This process produces a black and White print which is useful for most purposes but which is disadvantageous in certain respects. For example, it is frequently desirable in portrait photography to obtain photographic prints, especially of persons having dark skin pigmentation, wherein contrasts and highlights of the image are colored in brown tones rather than the above-described black and white tones.

Since normal toners, such as those containing only sulfide, e.g. sodium sulfide or thiourea and sodium hydroxide, produce black and white tones on direct positive film which is comprised of, for example, a silver bromide gelatin emulsion on a paper base, the need for a novel toning composition which would produce overall brown tones on such paper becomes apparent. Further, certain of the known toning agents are characterized by such a slow toning rate that a toning time of one minute or more is required, such a time for completion of the toning step being excessive. Accordingly, it is apparent that a fast-acting toning solution which produces over all warm brown tones would greatly advance the art of direct positive toning.

SUMMARY OF THE INVENTION In view of the above-described considerations, it is an object of this invention to provide novel toning compositions for silver bromide direct positive emulsions.

3,515,555 Patented June 2, 1970 A further object of the invention is the provision of a method of toning silver bromide direct positive emulsions which normally produce only black and white tones, which comprises treating such emulsions with the novel toning compositions of this invention whereby brown tones are obtained.

In accordance with the above objects, and other objects which will be apparent to those skilled in the art, the present invention provides novel toning compositions for direct positive papers comprising an inorganic sulfurcontaining compound, an alkali metal hydroxide, a thioamine or derivative thereof and an alkali metal iodide. It has unexpectedly been found that the novel toning composition of this invention produces a result dilferent than that obtained with the similar known toners containing thiourea and sodium hydroxide or odium sulfide. Thus, the toning activity of the combination of the components comprising the composition of the present invention behaves dilferently than would be expected from the activity of the individual compounds therein.

The direct positive photographic paper, with which the toning composition of the invention is used, is a silver bromide gelatin emulsion on a paper base (e.g. Super Speed Direct Positive Paper, Type 1703 sold by the Eastman Kodak Co). Such a paper, after normal exposure, development, bleaching, clearing, re-exposure and re-developing in the original developer, produces a black and white print.

As described above, the toning composition of the present invention comprises (1) an inorganic sulfur-containing compound, (2) an alkali metal hydroxide or alkali metal compound which will react in solution to produce the hydroxide, (3) a thioamine or derivatives thereof and (4) an alkali metal iodide.

Although liver of sulfur is preferably utilized as the inorganic sulfur-containing compound in the toning composition of the invention, an appropriate amount of sodium tetrasulfide solution may be utilized in lieu thereof. Liver of sulfur is prepared by the fusion of potassium carbonate and sulfur and contains chiefly a mixture of potassium sulfide and polysulfides. Not less than about 12.8% sulfur as sulfi-de is present. The inorganic sulfurcontaining compound or mixture is present in an amount of from about 2 g./l. to about g./l. of solution. Preferably, thi first component is present in an amount of from about 5 to 10 g./l. of solution.

The second component, eg an alkali metal hydroxide, utilized in the composition of the invention is preferably sodium hydroxide or potassium hydroxide although other alkali metal hydroxides or alkaline compounds which will react to yield such alkali metal hydroxides, such as trisodium phosphate may be used in lieu thereof. This component is present in a concentration of from about 1.0 g./l. to 70 g./l. but is preferably present in the range of from about 5.0 to 10.0 g./l.

The third component of the toning composition is a thioamine such as thiourea, acetyl thiourea, alkyl thiourea or a derivative thereof, such as appropriate amounts of thiamides, e.g. thioacetamide, thioacetanilide and the like. This component is preferably present in an amount of from about 0.5 g./l. to about 15 g./l. but high and lower concentrations may be utilized. Thus, a concentration of from about 1.0 to 1.5 g./l. produces beneficial results.

The fourth component of the composition of the invention is an alkali metal iodide such as sodium iodide, potassium iodide or the like in a concentration of from about 1.0 to 15 g./l. Best results are, however, obtained in the range of about 2.0 to 3.0 g./l.

The unexpected production of warm, brownish tones on silver bromide emulsions, particularly direct positive silver bromide emulsions which undergo formation of black image tones with conventional developers, becomes apparent when it is considered that the combination of an inorganic sulfur-containing compound and an alkali metal hydroxide produce only a neutral black tone and the use of liver of sulfur alone produces unpleasant red-brown tones with yellowish-brown middle density tones. It is only upon addition of a thioamine or derivative thereof, e.g. thiourea, and an alkali metal iodide and the proper balance thereof that a warm reddish-brown hue is obtained throughout the density scale.

Although normal toning time for the composition of the invention is about 10 seconds, longer times can be used with the concomitant formation of slightly colder tones. It has been found that the toning rate varies directly with the concentration of inorganic sulfur-containing compound and alkali metal hydroxide in the composition.

The toning composition of the invention is useful at temperatures of from about 55 to 90 F., although 75 F. is considered to produce the most beneficial results.

The invention will be more fully illustrated by the following examples which describe specific formulations of the toning compositions and their efiect on direct positive silver bromide photographic emulsions.

EXAMPLE 1 One liter of a concentrated toning composition of the invention is prepared by dissolving 250 g. liver of sulfur, 200 g. sodium hydroxide, 40 g. thiourea and 80 g. potassium iodide in approximately 816 g. distilled water.

The composition has a specific gravity, at 70 F. of approximately 1.386. For toning purposes, the concentrate is diluted with distilled water in a ratio of approximately 1 part concentrate to about 30 parts water. Good results will also be obtained using much more concentrated solutions.

EXAMPLE 2 A gelatin-based, direct positive, silver bromide photographic emulsion (Kodak Type 1703) is coated onto a paper support and dried. The emulsion of the coated support thus produced is exposed to light or other activating radiation of suitable intensity for forming a latent image on the emulsion and the emulsion is then developed, rinsed and then bleached in a dichromate/sulfuric acid bath. After bleaching, the emulsion is rinsed and cleared in a sodium bisulfite/sodium sulfite solution and re-developed using a conventional 2% sodium sulfide redeveloper. The direct positive print thus produced is toned in gradations of black and white.

EXAMPLE 3 The silver bromide emulsion described in Example 2 is exposed to light in order to form a latent image and then developed as set forth in Example 2, substituting for the sodium sulfide re-developer used therein the composition described in Example 1. The positive print formed is characterized by pleasing reddish-brown tones.

EXAMPLE 4 The direct positive emulsion of Example 2 is exposed and re-developed utilizing an aqueous toning solution containing 8.0 g./l. liver of sulfur and 6.5 g./l. sodium hydroxide. The positive print is characterized by a neutral black tone.

EXAMPLE 5 The emulsion of Example 2 is exposed and re-developed utilizing an aqueous toning solution containing 8 g./l. liver of sulfur. The positive print is characterized by unpleasant tones of red-brown and yellow-brown.

EXAMPLE 6 A toning solution is prepared as described in Example 1, substituting sodium tetrasulfide for liver of sulfur. A

4 direct positive paper (Kodak Type 1703) is exposed and developed utilizing each toning solution. The positive print is characterized by pleasing warm, brown tones.

EXAMPLE 7 A toning solution is prepared as described in Example 1, substituting thioacetamide for thiourea. Exposure and processing of Kodak Type 1703 Direct Positive Paper with this composition produces the desired image tones of a warm, brownish hue.

EXAMPLE 8 A direct positive, silver bromide emulsion coated on a paper base (Kodak Type 1703) was developed for 60 seconds in an MQ developer at 70 F., rinsed in Water for 15 seconds, bleached for 30 seconds, rinsed again for 15 seconds, cleared for 30 seconds and again rinsed in water for 30 seconds. Redevelopment with conventional sodium sulfide re-developer gave warm black tones throughout the image.

EXAMPLE 9 Upon substituting the composition of Example 1 in the re-development process illustrated in Example 8, the direct positive paper produced the desired warm reddish-brown tones of even density throughout the image.

Instead of the paper support described in the above specific examples, the present invention contemplates the use of other well-known photographic coating support materials such as films of cellulose esters, vinyl polymers, polyamides and halogenated olefinic polymers as well as metal film supports, textiles and glass plates.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described above and in the appended claims.

We claim:

1. A toning composition for direct positive silver bromide photographic paper which comprises:

(a) an alkali metal sulfide (b) a substance selected from the group consisting of an alkali metal hydroxide or an alkali metal salt which will produce a hydroxide upon hydrolysis (c) a thioamide, including for example: thiourea,

acetyl thiourea, alkyl thiourea, or a derivative thereof (d) an alkali metal iodide,

Whereas this composition is dissolved in water in the following proportions:

(a) 2-80 grams per liter (b) l-70 grams per liter (c) .515 grams per liter ((1) 1-15 grams per liter 2. A composition as defined in claim 1 wherein (a) is selected from the group consisting of liver of sulfur or sodium tetrasulfide.

3. A composition as defined in claim 1 wherein (b) is sodium hydroxide.

4. A composition as defined in claim 1 wherein (c) is thiourea.

5. A composition as defined in claim 1 wherein (d) is potassium iodide.

6. A toning solution for direct positive silver bromide photographic paper consisting essentially of the following components dissolved in water:

(a) about 8 grams per liter of liver of sulfur (b) about 6.5 grams per liter of sodium hydroxide (0) about 1.3 grams per liter of thiourea and (d) about 2.6 grams per liter of potassium iodide.

7. In a process for the development of silver images References Cited resulting from the development of direct positive silver UNITED STATES PATENTS bromide emulsions WhlCh normally are characterized by black and white tones, the improvement which comprises 2,678,886 5/1959 F 96-52 treating said emulsion with the composition defined in 5 3,004,850 10/1961 Dlcklnson et 96 52 claim 1 whereby brown tones are obtained. 3,048,486 8/1962 Basch 96 52 8. In a process for the development of silver images resulting from the development of direct positive silver NORMAN TORCHIM Pnmary Examiner bromide emulsions which normally are characterized by E. KIMLIN, Assistant Examiner black and white tones, the improvement which comprises treating said emulsion With the composition defined US. Cl. X.R. in claim 6 whereby brown tones are obtained. 9658, 64 

